Extrusion coating polyethylene

THE REPUBLIC OF POLAND (12) TRANSLATION OF THE EUROPEAN PATENT (19) pl (ii) PL / EP 1836232

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Patent Office of the Republic of Poland (96) Date and number of the European patent application:

January 12, 2005 05700846.8 (97) The grant of the European patent was announced:

2011/06/15 European Patent Bulletin 2011/24 EP 1836232 B1 (13) T5 (51) Int.CI.

C08F 297/08 (2006.01)

C08L 23/08 (2006.01)

C08L 23/12 (2006.01) (54) Title of the invention:

Polyethylene for extrusion coating (30)

Priority:

(43) Application was announced:

On September 26, 2007 in the European Patent Bulletin No. 2007/39 (45) The following was announced about the submission of the translation of the patent:

November 30, 2011 News of the Patent Office 2011/11 (47) The following was announced about submitting the amended translation:

28.04.2017 News of the Patent Office 2017/04 (73) Patent holder:

Borealls Technology Oy, Porvoo, FI 10

CN, CO CN &lt;0 CO (72) Inventor (s):

ERKKI LAIHO, PORVOO, FI

MARKKU SAINIO, PORVOO, FI

KAROLIINA HAAPANIEMI, Linz, AT (74) Representative:

thing, pat. Eliza Stypińska

LDS Łazewski Depo i Wspólnicy Sp. K. ul. Okopowa 58/72 01-042 Warsaw

Attention:

Within nine months of the publication of the information on the grant of the European patent, any person may file an objection to the European Patent Office against the European patent granted. The objection must be submitted in the form of a written statement of reasons. It is considered brought only when the opposition fee has been paid (Art. 99 (1) of the Convention on the Grant of European Patents).

EP 1 836 232 B2 Z-8190/16

Polyethylene for extrusion coating

The present invention relates to a polymer composition suitable for extruded coatings and films, particularly cast films having good chemical and barrier properties, in particular a low water vapor transmission rate (WVTR) and low curl. Additionally, the present invention relates to a method for the preparation of a composition according to the invention and its use. Moreover, the present invention relates to a multi-layer material containing a polymer composition as well as processing said multi-layer material.

[0002] One of the largest and fastest growing methods of processing polyolefins is extrusion coating. The largest unit quantity of coated materials are various papers and cardboard, which are used in a variety of packaging applications. Other frequently coated material are polymeric films, cellophane, aluminum foil, frozen food wrapping paper, and various fabrics. One goal of improving coated articles is to reduce the Water Vapor Transmission Rate (WVTR) as much as possible. A coated material with a low water vapor transmission rate (WVTR) may, for example, provide much better protection of the packaged products. The desired requirement obviously applies not only to coated materials, but also to cast films used as packaging or containers. In both cases, a low water vapor transmission rate is required. Many efforts have been made to improve the water vapor transmission rate of coated materials as well as cast films. To date, several new polymer compositions have been developed and great efforts have been made to find suitable fillers to significantly improve barrier properties. In addition, various polymers such as cycloolefin copolymers (COCs) and liquid crystal polymers (LCPs) have been designed. However, these materials have the disadvantage of being expensive and having poor processing properties.

[0003] WO 00/71615 discloses for example the use of a bimodal high-density polyethylene (HDPE) with a melt index, MFR2, of 5 g / 10 min and a density of 957 kg / m3.³ for extrusion coating. No guidance is given on how to improve the water vapor transmission rate (WVTR).

[0004] WO 00/34580 describes a spacer for pressure sensitive adhesive labels. The spacer comprises a web of paper, a filled polymer layer, and an extruded material, e.g. polyethylene, on the reverse side of the paper carrier, and a spacer foil layer on top of the embossed material. The filled polymeric layer may be polyethylene and the filler may be inert particles such as silica, mica, clay, talc or titanium dioxide. The filler is present in an amount of 15 to 40 wt.%. composition.

[0005] US 4,978,572 describes a laminate film having three layers. The first layer comprises a thermoplastic resin and from 0.3 to 30 wt. white inorganic particles. The second one comprises an ethylene copolymer from 0.5 to 90 wt.%. substances with anti-blocking and antioxidant properties. The third one contains metallized thermoplastic. The anti-blocking material in the second layer may be silica or talc. Laminated film is defined as having good mechanical strength and good barrier properties.

[0006] DE 198 49 426 A1 discloses a bimodal polyethylene blend having a high mixing quality of less than 3 in accordance with ISO 13949 and a high environmental cracking strength of more than 150 hours. These polyethylene blends are successfully used in pressure-resistant pipes for the transport of gases, water and sewage. The low molecular weight component consists of an ethylene homopolymer or copolymer having a weight average molecular weight of 8,000 to 80,000 g / mol. The density of the low molecular weight component may be greater than 0.95 g / cm³. The high molecular weight component consists of an ethylene homopolymer or copolymer having a weight average molecular weight of at least 300,000 g / mol. The bimodal polyethylene blend may further contain up to 10 wt. auxiliary substances such as pigments.

[0007] Even though the prior art already has a number of products having good Water Vapor Transmission Rate (WVTR) coefficients, there is still a need to significantly improve these properties. One of the significant disadvantages of filler-containing polymer compositions that limit the water vapor transmission rate (WVTR) is the poor dispersion of fillers incorporated into the polymer matrix. Traditional mechanical introduction often results in poor dispersal as conventional fillers form multilayer aggregates due to incompatibility with the polymer matrix. One consequence of the described phenomenon is that the water vapor transmission rate (WVTR) varies significantly within the layer, leading to unsatisfactory mean WVTR values. Second, the poor dispersion of the fillers makes the polymer composition coating the materials curl easily. The uniform dispersion of fillers incorporated into the polymer composition should therefore significantly improve the water vapor transmission rate, and further improve the curl properties of the coated material.

[0008] It is therefore an object of the present invention to improve the water vapor transmission rate (WVTR).

[0009] The present invention is based on the finding that this object can be achieved by a polymer composition containing a polymer of low average molecular weight, allowing better and uniform dispersion of fillers incorporated into the polymer composition.

[0010] The present invention therefore provides a multimodal polymer composition as defined in claim 1.

[0011] Therefore, the polymer composition of the invention is multimodal with respect to the molecular weight distribution. "Multimodal or" multimodal distribution describes a frequency distribution that has several corresponding maxima. In particular, the phrase "the modality of a polymer refers to the shape of its molecular weight distribution (MWD) curve, that is, the appearance of a graph of the weight fractions of a polymer as a function of their molecular weights. The molecular weight distribution curve of a polymer produced in one polymerization step using a single monomer mixture, a single polymerization catalyst and under a single set of process conditions (i.e. temperature, pressure, etc.) shows one maximum, the width of which depends on the choice of catalyst, choice of reactor, process, etc., i.e. such a polymer is monomodal.

[0012] The inventive composition is characterized by a very low water vapor transmission rate (WVTR) as well as very low curl values ​​of the extrusion coated layers. These improved properties are achieved due to the much better dispersion of filler (C) in the mixture of polymer (A) and polyolefin (B) compared to a monomodal polymer having the same melt flow rate and density in both the extrusion coated layer and cast films.

[0013] Thus, the polymer composition of the invention is a multimodal polymer composition, including a bimodal polymer composition consisting of two different polymers having two different molecular weight distribution curves, which polymers are either mechanically or in situ mixed during their preparation. Preferably, the polymer composition is at least a bimodal, mechanically or in situ obtained blend of polyolefin (1) (as polymer (A)) and polymer (B). Since the bimodal blend may further contain additional polymer (A), the final polymer composition may also be Ina tri-mode.

[0014] Molecular weight distribution (MWD) is the relationship between the amounts of molecules in the polymer and the lengths of the individual chains. The molecular weight distribution (MWD) is often given as a numerical value that normally represents the weight average molecular weight (M_in) and number average molecular weight (M._n).

[0015] The weight average molecular weight (Mw) is the first steep slope of the plot of the weight of polymers in each molecular weight range against the molecular weight. In turn, the number average molecular weight (M._n) is the average molecular weight of the polymer expressed as the first sweep of the plot of the number of molecules in each molecular weight range against the molecular weight. In effect, it is the total molecular weight of all molecules divided by the number of molecules.

[0016] The weight average molecular weight (Mw) and the number average molecular weight (Mn) and the molecular weight distribution (MWD) are determined according to ISO 16014.

[0017] The weight average molecular weight (Mw) is the parameter of the average chain length of molecules. Small values ​​of M_in indicate that the chain length of the molecules is on average rather short. It has been found that the polymer mixture containing the polymer (A) with the Mw values ​​defined in claim 1 contributes inter alia to better barrier properties and better dispersion of the filler (C). This better dispersion improves the water vapor transmission rate (WVTR) as well as having a positive effect on curl resistance.

[0018] Thus, as a further requirement of the present invention, the multimodal polymer composition must contain at least one polymer (A) which is a wax and has a weight average molecular weight (Mw) of less than 10,000 g / mol. It is particularly preferred that the composition further comprises at least one polymer (A) having a weight average molecular weight (Mw) of 10,000 to 60,000 g / mol, more preferably 20,000 to 50,000 g / mol. The at least one wax (2) preferably has a weight average molecular weight (Mw) in the range of 500 to 10,000 g / mol.

[0019] Furthermore, preferably the polyolefin (1) is polyethylene or polypropylene, more preferably polyethylene. The polyolefin (1) can be a monopolymer or a copolymer. Preferably the polyolefin (1) is a propylene or ethylene monopolymer or copolymer, more preferably the polyolefin (1) is an ethylene monopolymer or copolymer. Most preferably the polyolefin (1) is low density polyethylene (LDPE), linear low density polyethylene (LLDPE) or linear medium density polyethylene (LMDPE). LDPE, LLDPE and LMDPE are equally suitable alternatives to polyolefins (1), e.g. where LLDPE or LMDPE is applicable, LDPE may also be used and vice versa.

[0020] The polymer (A) which is the wax (2) is preferably selected from one or more of the following materials:

(2a) a polypropylene wax having a weight average molecular weight (Mw) of less than 10,000 g / mol, more preferably in the range 500 to 10,000 g / mol, even more preferably in the range 1,000 to 9,000 g / mol, even more preferably in the range 2,000 to 8,000 g / mol. mol and most preferably in the range 4,000 to 8,000 g / mol or a polyethylene wax having a weight average molecular weight (Mw) of less than 10,000 g / mol, more preferably in the range 500 to 10,000 g / mol, even more preferably in the range 1,000 to 9,000 g / mol. even more preferably in the range of 2,000 to 8,000 g / mol and most preferably in the range of 4,000 to 8,000 g / mol, and (2b) an alkyl ketene dimer wax having a weight average molecular weight (Mw) of less than 10,000 g / mol, more preferably less than 5,000 g / mol , even more preferably less than 1000 g / mol. In turn, the alkylketene dimer wax has a weight average molecular weight (Mw) of at least 100 g / mol. Most preferably the alkyl ketene dimer wax has a weight average molecular weight (Mw) in the range of 250 to 1000 g / mol.

[0021] The terms "at least one polymer (A), at least one polyolefin (1) or" at least one wax (2) "indicate that more than one polymer (A), polyolefin (1) may be present in the multimodal polymer composition. or wax (2). Preferably, one, two or three different polymers (A) as defined above are used in the multimodal polymer composition. It is even more preferred that only wax (2) is used as component (A), preferably a polypropylene wax (2a) or an alkyl ketene dimer wax (2b) as defined above. In case component (A) comprises a polyolefin (1) as defined above, wax (2) is present in the multimodal polymer composition as a further polymer (A). In such cases, the multimodal composition is preferably a trimodal composition comprising a polyolefin (1), a wax (2), and a polyolefin (B) having differently located peaks in the molecular weight distribution, e.g. having different weight average molecular weights (M_in). The use of wax (2) has the advantage that the amorphous region of the polymer matrix, which may be a blend of polyolefin (1) and polyolefin (B), is filled, thereby improving the barrier properties.

[0022] The final polymer composition has a specific density of 940 kg / m3³ or less, but also polymer (A) has a specific density of less than 945 kg / m3³. Preferably, polyolefin (1), if used as polymer (A), has a density less than 945 kg / m3.³, more preferably in the range of 905 to 935 kg / m3³, even more preferably in the range of 910 to 930 kg / m³and most preferably in the range of 915 to 925 kg / m2³. Preferably, the polyolefin (1) is linear low density polyethylene (LLDPE) or linear medium density polyethylene (LMDPE). In turn, also low-density polyethylene (LDPE) produced in the high-pressure process of free-radical polymerization is also used as a polyolefin (1). Linear Low Density Polyethylene (LLDPE) or Linear Medium Density Polyethylene (LMDPE) are produced by the process described below for polyolefin (B).

[0023] The molecular weight distribution (MWD) of the polymer composition is further characterized by the melt flow rate (MFR) according to ISO 1133 at 190 ° C. The melt flow rate (MFR) depends primarily on the average molecular weight. This is because long-chain molecules produce a material that is less flowable than short-chain molecules.

[0024] An increase in molecular weight means a decrease in MFR value. The melt flow rate (MFR) is measured in g / 10 min of the polymer flow under specific temperature and pressure conditions and is a measure of the polymer viscosity which in turn is influenced for each type of polymer by its molecular weight distribution as well as the degree of branching. The melt flow rate when measured with a load of 2.16 kg (ISO 1133) is denoted as MFR2. In contrast, the melt flow rate measured with a load of 5 kg (ISO 1133) is denoted as MFRs.

[0025] In a case where polymer (A) is polyolefin (1), an MFR2 in the range of 1.0 to 20.0 g / 10 min is preferred, and more preferably in the range of 2.0 to 15.0 g / 10 min, for example in the range of 3.0 to 10.0 g / min. According to one embodiment of the invention, polyolefin (1) is linear low density polyethylene (LLDPE) or linear medium density polyethylene (LMDPE) with MFR? given above. In turn, polyolefin (1) may also be low density polyethylene (LDPE) having a density within the range mentioned in this paragraph. Low Density Polyethylene (LDPE) is produced by a high pressure free radical polymerization process. In turn, linear low density polyethylene (LLDPE) or linear medium density polyethylene (LMDPE) are produced by the process described for polyolefin (B).

[0026] In the case where polymer (A) is an ethylene monopolymer, preferably the ethylene monopolymer contains less than 0.2 mole%, preferably less than 0.1 mole% and most preferably less than 0.05 mole% of units derived from α- olefins other than ethylene. Particularly preferably, polymer (A) is an ethylene copolymer, more preferably having a weight average molecular weight of from 10,000 g / mol to 60,000 g / mol, even more preferably from 20,000 to 50,000 g / mol. Even more preferably, polymer (A) is an ethylene copolymer having a density of 905 to 935 kg / m3³, more preferably 910 to 930 kg / m2³, most preferably 915 to 925 kg / m2³ and having a melt flow rate MFR? 1.0 to 20.0 g / 10 min, more preferably 2.0 to 15.0 g / 10 min, most preferably 3.0 to 10.0 g / min. Preferably, the ethylene copolymer comprises, and more preferably consists of, comonomer units as defined below for LLDPE. It is particularly advantageous if the ethylene copolymer fulfills all of the above-mentioned properties simultaneously.

[0027] In the case where the polymer (A) is a wax, namely a polypropylene wax or a polyethylene wax, preferably the wax has a weight average molecular weight (Mw) in the range of 500 to 10,000 g / mol, more preferably in the range of 1000 to 9000 g / mol. mol, even more preferably in the range of 2000 to 8000 g / mol and most preferably in the range of 4000 to 8000 g / mol. Further preferred weight average molecular weight ranges (M._in) a wax, especially a polypropylene wax or a polyethylene wax, is in the range of 4000 to 7000 g / mol, even more preferably in the range of 5000 to 6000 g / mol, and most preferably in the range of 5,300 to 5,400 g / mol. Moreover, preferably the wax, especially polypropylene wax or polyethylene wax, has an average molecular weight of from 9100 to 40,000 g / mol, more preferably from 500 to 20,000 g / mol, and most preferably from 10,000 to 12,000 g / mol. In addition, preferably the wax, especially polypropylene wax or polyethylene wax, has a number average molecular weight (M_n) from 100 to 20,000 g / mol, more preferably from 500 to 3000 g / mol.

[0028] Moreover, preferably the wax, especially polypropylene wax or polyethylene wax, has a characteristic molecular weight distribution (MWD) which is the relationship between the amounts of molecules in the polymer and the lengths of the individual chains. The molecular weight distribution (MWD) is given as a numerical value that normally represents the quotient of the weight average molecular weight and the number average molecular weight (M_in/ M_n). Preferably the wax, especially polypropylene wax or polyethylene wax, has a MWD in the range of 1 to 5, more preferably in the range of 1.5 to 4.

[0029] Furthermore, preferably the wax, especially polypropylene wax or polyethylene wax, has a DSC softening point below 150 ° C, more preferably below 140 ° C, even more preferably in the range from 95 to 130 ° C, most preferably in the range from 105 to 115 ° C.

In the case where a wax, namely an alkyl ketene dimer, is used as polymer (A), preferably the weight average molecular weight (M_in) of the wax is greater than 100 g / mol. In turn, preferably the weight average molecular weight of the wax is less than 10,000 g / mol, more preferably less than 5,000 g / mol, even more preferably less than 1000 g / mol. Preferred ranges for the weight average molecular weight (M._in) of the wax is from 100 to 10,000 g / mol, more preferably from 250 to 1000 g / mol. Additionally, preferably the wax has a number average molecular weight (M._n) from 100 to 20,000 g / mol, more preferably in the range from 100 to 800 g / mol. Additionally, preferably the wax has a softening point as determined by DSC analysis below 140 ° C, more preferably below 100 ° C. A preferred range of the softening point as determined by DSC analysis is 50 to 90 ° C, more preferably 50 to 70 ° C.

[0031] As a further requirement, according to the present invention, polyolefin (B) has a higher weight average molecular weight (Mw) than polymer (A). Polyolefin (B) has a weight average molecular weight (Mw) greater than 80,000 g / mol, more preferably less than 100,000 g / mol. The upper range for the weight average molecular weight of the polyolefin (B) is not greater than 300,000 g / mol, more preferably not greater than 200,000 g / mol. A preferred range for the weight average molecular weight of polyolefin (B) is 80,000 to 300,000 g / mol, more preferably 100,000 to 200,000 g / mol. Preferably, the polyolefin (B) is linear low density polyethylene (LLDPE) or linear medium density polyethylene (LMDPE) which has preferably been produced in a medium pressure process in the presence of a polymerization catalyst (i.e. a Ziegler-Natta catalyst or a metallocene catalyst). Linear Low Density Polyethylene (LLDPE) and Linear Medium Density Polyethylene (LMDPE) have a density less than 945 kg / m3³, more preferably in the range of 905 to 935 kg / m3³, even more preferably in the range of 910 to 930 kg / m³and most preferably in the range of 915 to 925 kg / m2³. However, low-density polyethylene (LDPE) may also find use as polyolefin (B). Low-density polyethylene (LDPE) has the same density ranges as LLDPE or LMDPE mentioned in this paragraph and is a product of a high pressure polymerization process characterized by a highly branched chain structure. LDPE, LLDPE and LMDPE are also suitable alternatives to polyolefins (B), e.g. where LLDPE or LMDPE is applicable, LDPE may also be used and vice versa.

[0032] According to the invention, more than one polyolefin (B) may be used. Therefore, the invention also includes the possibility of using any mixture of linear low density polyethylene (LLDPE), linear medium density polyethylene (LMDPE) and low density polyethylene (LDPE).

[0033] The MFRz of polyolefin (B) is preferably in the range of 1.0 to 20.0 g / 10 min, more preferably in the range of 2.0 to 15.0 g / 10 min, e.g. in the range of 3.0 to 10, 0 g / 10 min. It is particularly preferred that linear low density polyethylene (LLDPE) and linear medium density polyethylene (LMDPE) have these flow characteristics. Also the low density polyethylene (LDPE) useful as polyolefin (B) may have the flow characteristics as given in this paragraph.

[0034] Preferably the polyolefin (B) is polyethylene. In case the polyolefin (B) is polyethylene, it may be an ethylene monopolymer or an ethylene copolymer. In case an ethylene monopolymer is used as polyolefin (B), preferably an ethylene monopolymer as defined for polymer (A) is used. In case an ethylene copolymer is used as polyolefin (B), preferably an ethylene copolymer as defined below is used. Particularly preferably, the polyolefin (B) is low density polyethylene (LDPE), linear low density polyethylene (LLDPE) or linear medium density polyethylene (LMDPE).

[0035] According to one embodiment of the invention, the polymer composition of the invention is a linear low density polyethylene (LLDPE) comprising a polyolefin (1) (polymer (A)) as the low molecular weight LLDPE fraction and polyolefin (B) as the high molecular weight LLDPE fraction. This linear low density polyethylene (LLDPE) may be a mechanically obtained blend, preferably an in situ blend in a multistage process. Preferably said composition comprises wax (2) as further polymer (A).

[0036] The polymer composition as defined above comprises from 1 to 50 wt. % of polymer (A), from 40 to 90 wt. % of polyolefins (B) and from 1 to 50 wt. % of filler (C), more preferably 5 to 40 wt.%, and most preferably 10 to 35 wt.%. In case the polymer composition is produced by an in situ polymerization process, e.g. a process involving sequential steps using the reactors connected in series and described above, preferably the polymer (A) may range from 40 to 60 wt%, more preferably 49 to 55 wt%. in the polymer blend without filler (C). In turn, preferably in such a polymer blend, polyolefin (B) is in the range of 60 to 40 wt%, more preferably 51 to 45 wt%. Preferably, the total polymer composition comprises from 50 to 90 wt. % of said polymer blend and from 1 to 50 wt. Filler (C), more preferably 5 to 40 wt.% And most preferably 10 to 35 wt.%.

[0037] In the case where polymer (A) and polyolefin (B) are mechanically mixed, preferably the polymer (A) may range from 1 to 30 wt%, and more preferably from 1 to 20 wt%. total polymer composition. These ranges especially apply when only wax (2) is used as polymer (A).

[0038] A last requirement according to the present invention is that the multimodal polymer composition additionally comprises a filler (C). Any filler having a positive effect on the water vapor transmission rate (WVTR) can be used. Preferably, the filler has a lamellar structure like clay, mica or talc. More preferably, the filler is finely pulverized. The finely powdered filler consists of 95 wt. % of particles having a size less than 10 µm and about 20-30 wt.%. particles having a size less than 1 µm. All layered materials can be used in the present invention as long as they are dispersible in the polymer composition. The filler may be a clay-based compound or a submicron filler such as talc, calcium carbonate or mica, which are typically treated, e.g. by grinding, to obtain small, i.e. submicron dimensions.

[0039] Preferably, the filler (C) is a silicate-based inorganic layered material, more preferably the filler (C) is a clay-based compound. The clay compounds are dispersed throughout the polymer composition during mixing of the polymer compositions so that individual lamellae in the layered structure are separated.

[0040] In a further preferred embodiment of the invention, the filler (C) is a material or a mixture of clay-based inorganic layered materials, preferably silicate-based. Useful clay materials include natural, synthetic, and modified phyllosilicates. Natural clays include smectites such as montmorillonite, hectorite, mica, vermiculite, bentonite. Synthetic clays include synthetic mica, synthetic saponite, synthetic hectorite. Modified clays include fluorinated montmorillonite and fluorinated mica.

[0041] Of course, the filler (C) may also contain ingredients including a mixture of different fillers, such as mixtures of clay-based fillers and talc.

[0042] The layered silicates may be organophilized by chemical modification, such as cation exchange with cationic ammonium or phosphonium complexes, prior to dispersion in the polymer composition. These cationic complexes get sandwiched between the clay layers.

[0043] Preferably, a smectite clay is used which includes montmorillonite, beidelite, nontronite, saponite as well as hectorite. The most preferred smectic clay is montmorillonite.

[0044] Preferably also talc is used as filler (C).

[0045] Density affects most physical properties like stiffness, impact strength and the optical properties of the end products. Thus, according to the present invention, the density of the polymer composition is 940 kg / m3³ or less. More preferably the density is in the range of 905 to 935 kg / m3³, even more preferably in the range from 910 to 930 kg / m³and most preferably in the range from 915 to 925 kg / m2³.

[0046] The ranges and values ​​given for the density throughout the invention apply to the pure polymer composition and do not include any excipients, especially no filler (C). The density is determined according to ISO 1183-1987.

[0047] Moreover, the polymer composition without any excipient, preferably without filler (C), has a melt index MFR2 according to ISO 1133 at 190 ° C of 5 to 20 g / 10 min, more preferably 7 to 15 g / 10 min. .

Preferably, the polymer composition without any excipient, preferably without filler (C), has a melt flow index MFRs according to ISO 1133 at 190 ° C of 20 to 40 g / 10 min, more preferably 25 to 35 g / 10 min. .

[0049] Furthermore, it is preferred that the melt flow ratio, which is the ratio of the two melt flow rates measured with the same polymer at two different loads, lies within a specific range. A preferred particular range is 2.5 to 4.5, preferably 2.7 to 4.0, for the melt flow ratio MFR5 / MFR2.

[0050] Further characterization of the molecular weight distribution (MWD), which is the relationship between the amounts of molecules in the polymer and the lengths of the individual chains, should also be considered. The molecular weight distribution distribution is a number value derived from the quotient of the weight average molecular weight and the number average molecular weight (M_in/ M_n). In the present invention, preferably the polymer composition without any excipient, preferably without filler (C), has M_in/ M_n of 8 to 25, and more preferably of 10 to 20.

[0051] Further additives are used, for example inorganic auxiliaries, known in the field of coatings and films as extrusion auxiliaries and agents.

[0052] For better adhesion of the coating and the substrate, the polymer is preferably oxidized. Consequently, it is preferred that the polymer composition comprises antioxidants and processing stabilizers in an amount of less than 2000 ppm, more preferably less than 1000 ppm, and most preferably no more than 700 ppm. Hence, the antioxidants may be selected from those known in the art, such as e.g. including hindered phenols, secondary aromatic amines, thioethers or other sulfur-containing compounds, phosphites and the like, including mixtures thereof.

[0053] It has been found that the polymer composition described above has a very low water vapor transmission rate (WVTR). Furthermore, the composition adheres well to the substrate, especially aluminum, without the need for an adhesive layer between the substrate and the coating. Moreover, the curl tendency of the coated article is significantly reduced for the polymer composition compared to the polymer itself. These advantageous effects could only be obtained because the miscibility of the polymer and filler is significantly greater for a multimodal or bimodal polymer containing a low molecular weight polymer fraction compared to a polymer having the same melt index and density.

[0054] In one preferred embodiment of the invention, the multimodal composition comprises as polymer (A), which is the low molecular weight fraction, a polyolefin (1), more preferably low density polyethylene (LDPE) or linear low density polyethylene (LLDPE). The polyolefin (B), which is the high molecular weight fraction, is linear low density polyethylene (LLDPE). This composition comprises a further polymer (A) which is a wax (2) as defined above. This composition can be produced in situ or mechanically agitated. The preferred properties of polymer (A), in particular polyolefin (1), wax (2) and polyolefin (B) are as stated above. In case the composition comprises two polymers (A), namely polyolefin (1) and wax (2), preferably the amount of wax (2) in the total unfilled composition (C) is from 1 to 30 wt%, more preferably from 1 to 20 wt%. % by weight and most preferably from 1 to 10% by weight. In turn, the composition comprises from 70 to 99 wt%, more preferably from 80 to 99 wt%, and most preferably from 90 to 99 wt%. LLDPE derived from polymer (A) and polyolefin (B). When the composition comprises LDPE, it is preferred that wax (2) is present in an amount from 1 to 30% and the LDPE is at least derived from polymer (B) and optionally polymer (A) and is present in an amount from 70 to 99 wt%. in the whole composition without filler (C).

[0055] In another preferred embodiment of the invention, the polymer composition is produced in situ by a process, preferably a process the successive steps of which are carried out using reactors connected in series as described above. Preferably, polymer (A) is produced in a loop reactor, while polyolefin (B) is produced in a gas-phase polymerization reactor in the presence of polymer (A). Thus, preferably the multimodal polymer is at least one bimodal polymer. More preferably, both polymer (A) and polyolefin (B) are polyolefins. The polymer composition in this embodiment comprises from 50 to 99 wt. of linear low density polyethylene (LLDPE) having a multimodal, more preferably bimodal molecular weight distribution (MWD) and more preferably from 1 to 50 wt. filler (C), preferably a plaque or sheet filler such as mica or talc as described above.

[0056] Still, when the description refers to LLDPE, it means that a multimodal, preferably bimodal LLDPE is used that contains a low molecular weight (LMW) fraction which is polymer (A) (polyolefin (1)), and a high molecular weight (HMW) fraction that is polymer (B).

Preferably, the linear low density polyethylene (LLDPE) has an MFR2 of from 1.0 to 20.0 g / 10 min, more preferably in the range from 2.0 to 15.0 g / 10 min, and most preferably from 3.0 up to 10.0 g / min. Preferably the linear low density polyethylene (LLDPE) has a density below 945 kg / m3³ and is in the range of 905 to 935 kg / m3³, more preferably in the range from 910 to 930 kg / m2³most preferably in the range from 915 to 925 kg / m³. If the melt flow rate of linear low density polyethylene (LLDPE) is less than 1 g / 10 min, high productivity is not obtained. On the other hand, if the melt flow rate MFR2 is greater than 20, the melt strength of the polyethylene is deteriorated.

[0058] Furthermore, preferably the linear low density polyethylene (LLDPE) has an MFRs of 20 to 40 g / 10 min, and preferably a melt flow ratio MFRs / MFR2 of 2.5 to

4.5, more preferably from 2.7 to 4.0. Furthermore, it is preferred that the linear low density polyethylene (LLDPE) has a weight average molecular weight (Mw) of 50,000 to 150,000 g / mol, more preferably in the range of 60,000 to 100,000 g / mol, and preferably has a weight average molecular weight quotient and a number average molecular weight ratio. M._in/ M_n of 8 to 25, and more preferably 10 to 20.

[0059] Furthermore, the linear low density polyethylene (LLDPE) comprises comonomers selected from the group consisting of C3 α-olefins, C4 α-olefins, Cs α-olefins, Ce α-olefins, C7 α-olefins, Cs oolefins, C9 α-olefin, C10 α-olefin, Cu α-olefin, C12 α-olefin, C13 α-olefin, C14 α-olefin, Cis o-olefin, Cie α-olefin, C17 α-olefin, Cis α-olefin, C19 α-olefin, C20 α-olefin. Particularly preferred are oolefins selected from the group consisting of propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 6-methyl- 1-heptene, 4-ethyl-1-hexene, 6-ethyl-1-octene and 7-methyl-1-octene. Even more preferably, the α-olefins are selected from the group consisting of 1-butene, 4-methyl-1-pentene, 1-hexene and 1-octene.

[0060] One requirement in a preferred embodiment is that the polymer composition is a linear low density polyethylene (LLDPE) with a comonomer unit content in the polymer, preferably 0.1 to 1.0 mole%, more preferably 0.15 to 0 , 5 mole%.

[0061] Preferably the unfilled linear low density polyethylene (LLDPE) (C) comprises from 40 to 60 wt.%, More preferably from 49 to 55 wt. % of polymer (A) and from 60 to 40 wt.%, more preferably from 51 to 45 wt.%. polyolefins (B).

[0062] As stated above, preferably the linear low density polyethylene (LLDPE) comprises a LMW fraction contained in the polymer (A). More preferably, polymer (A) is an olefin (1), most preferably an ethylene copolymer containing α-olefins other than ethylene and mentioned above. Furthermore, preferably the linear low density polyethylene (LLDPE) polymer (A) has a weight average molecular weight of from 10,000 g / mol to 60,000 g / mol, even more preferably from 20,000 to 50,000 g / mol. Even more preferably, the linear low-density polyethylene (LLDPE) polymer (A) has a density of 905 to 935 kg / m3.³, more preferably from 910 to 930 kg / m2³. Furthermore, preferably the linear low density polyethylene (LLDPE) polymer (A) has a melt flow rate MFR2 of 1.0 to 20.0 g / 10 min, more preferably 2.0 to 15.0 g / 10 min, most preferably 3, 0 to 10.0 g / min.

[0063] Preferably the polyolefin (B) as the linear low density polyethylene (LLDPE) is an ethylene copolymer containing one or more α-olefins as mentioned above. Accordingly, preferably the amount of comonomer units in the polyolefin (B) is from 2.0 to 15.0 mol%, more preferably from 3.0 to 10.0 mol%. Furthermore, preferably the polyolefin (B) in linear low density polyethylene (LLDPE) has a weight average molecular weight of 80,000 to 300,000 g / mol, more preferably 100,000 to 200,000 g / mol.

[0064] The filler (C) and other additional components in linear low-density polyethylene (LLDPE) are used identically as listed and described above. Particularly preferably, in addition to LLDPE, a wax (2), more preferably a polypropylene wax (2a) or an alkyl ketene dimer (2b) as defined above, is used as the additional polymer (A).

[0065] In the case where two polymers (A) are used, namely polyolefin (1) and wax (2), the amount of wax (2) is from 1 to 30 wt%, more preferably from 2 to 20 wt%, % and most preferably from 1 to 10 wt.%. total composition without filler (C). In turn, the unfilled composition (C) comprises from 70 to 99 wt%, more preferably from 80 to 88 wt%, and most preferably from 90 to 99 wt%. LLDPE derived from polymer (A) and polyolefin (B).

[0066] Another preferred embodiment of the present invention is a polymer composition in which polymer (A) and polyolefin (B) are mechanically mixed. Thus, at least one polymer (A) is a wax (2), more preferably a polypropylene wax or an alkyl ketene dimer wax.

[0067] In the case of the polymer (A) where a polypropylene wax is used, the wax preferably has a weight average molecular weight (M_in) from 100 to 50,000 g / mol, more preferably from 100 to 10,000 g / mol, and most preferably from 5,000 to 6,000 g / mol. Moreover, it is preferred that the average molecular weight of the polypropylene wax ranges from 100 to 60,000 g / mol, and more preferably from 100 to 10,000 g / mol. Preferably the polypropylene wax has a number average molecular weight (M._n) from 100 to 2000 g / mol, more preferably from 500 to 3000 g / mol. The softening point of the polypropylene wax as determined by DSC analysis is preferably from 95 to 130 ° C, more preferably from 105 to 115 ° C.

Preferably, the polypropylene wax is mechanically mixed with the ethylene polymer polyolefin (B) having an MFR2 of 6.5 to 8.5 g / 10 min, more preferably 7 to 8 g / 10 min and a density of 900 to 940 kg / m³, more preferably from 915 to 925 kg / m2³. particularly preferably the polyolefin (B) is low density polyethylene (LDPE) or linear low density polyethylene (LLDPE) as described above.

[0069] The mechanically blended polymer containing talc as filler (C) and CaO as the water-absorbing component preferably has a density in the range of 1000 kg / m3.³ up to 1300 kg / m³, more preferably from 1150 to 1200 kg / m2³ and a melt flow rate MFR2 preferably from 8 to 9.5 g / 10 min, and more preferably from 8.5 to 9.0 g / 10 min.

[0070] Another preferred alternative of mechanically blending wax (2) with polyolefin (B) is the use of an alkyl ketene dimer as the wax (2). Preferably, said alkyl ketene dimer has a weight average molecular weight (M._in) from 300 to 400 g / mol, more preferably from 320 to 350 g / mol. Preferably, the z-average molecular weight of the alkyl ketene dimer is from 300 to 400 g / mol, more preferably from 360 to 390 g / mol. Preferably, said alkyl ketene dimer has a number average molecular weight (M._n) from 200 to 450 g / mol, more preferably from 280 to 300 g / mol. Moreover, the softening point of the alkyl ketene dimer as determined by DSC analysis is preferably from 55 to 70 ° C, more preferably from 60 to 65 ° C.

[0071] For the polyolefin (B), the same ethylene polymer is used as specified for the mechanically obtained blend containing polypropylene wax.

[0072] The density of the mechanically agitated polymer composition comprising the alkyl ketene dimer as defined above, the ethylene polymer (B) as defined above, the filler (C) and the water-absorbing component, is preferably from 1050 to 1300 kg / m3.³and more preferably from 1150 to 1250 kg / m2³. Melt Flow Rate MFR? of said polymer composition is preferably from 12.5 g / 10 min to 14.5 g / 10 min, and more preferably from 13.0 g / 10 min to 14.0 g / 10 min. In a preferred embodiment, talc is used as filler (C) and the humectant is CaO.

[0073] Furthermore, the present invention also relates to a method for the preparation of a multimodal composition as defined above.

[0074] A multimodal or at least bimodal, for example bimodal or trimodal, polymer can be produced by blending two or more monomodal polymers having differently spaced maxima in the molecular weight distributions. The mixture can be obtained mechanically, e.g. analogously to the principle of mechanical mixing known in the art. Alternatively, a multimodal or at least bimodal polymer composition, e.g. bimodal or trimodal, may be produced by polymerization under conditions which result in a multimodal or at least bimodal polymer composition, e.g. bimodal or trimodal, e.g. using a catalyst system for mixtures with two or more catalytic sites, using a two or more stage polymerization process under different conditions at different stages (i.e. different temperatures, pressures, polymerization medium, hydrogen partial pressures, etc.). When making the polymer by such a post-reaction process, i.e. using reactors connected in series, and using different conditions in each reactor, the different polymer fractions produced in the different reactors will have their own molecular weight distributions, which may differ significantly from one another. The molecular weight distribution curve of the final polymer obtained can be viewed as superimposed molecular weight distribution curves of the polymer fractions which will accordingly exhibit two or more different peaks, or at least one significantly extended maximum, as compared to the individual fraction curves.

[0075] A polymer showing such a molecular weight distribution curve is called multimodal, trimodal or bimodal.

[0076] Multimodal polymers can be made by a number of methods which are described, e.g. in WO 92/12182 and WO 97/22633.

[0077] The multimodal polymer is preferably produced in a multistage process in a multistage reaction sequence as described in WO 92/12182. The content of this document is hereby incorporated by reference in its entirety.

[0078] It is known to produce multimodal or at least bimodal, e.g. bimodal or trimodal polymers, preferably multimodal or bimodal olefin polymers such as multimodal or bimodal polyethylenes, in two or more series connected reactors whereby compounds (A) and (B) can be produced in any order.

[0079] According to the present invention, the main polymerization steps are preferably carried out as a combination of suspension polymerization / gas phase polymerization. The suspension polymerization is preferably carried out in so-called loop reactors. Optionally, and more preferably, the suspension polymerization step passes through a gas phase stage.

[0080] Optionally and more preferably, the main polymerization steps may be preceded by a pre-polymerization, in which case up to 20 wt.%, Preferably 1-10 wt.%, More preferably 1-5 wt.% Is produced. the total amount of the polymer composition. At the point of prepolymerization, all of the catalyst is fed to the loop reactor and the polymerization is carried out as a suspension polymerization. This polymerization leads to the production of smaller particles in subsequent reactors and to a more homogeneous product finally. Such a pre-polymerization is described, for example, in WO 96/18662.

[0081] Generally, a technique is used to obtain a polymer composition - multimodal or at least bimodal, for example bimodal or trimodal, wherein a Ziegler-Natta catalyst or a metallocene catalyst is used in several successive polymerization reactors. For example, in the production of a bimodal high-density polyethylene composition, the first ethylene polymer is produced in the first reactor under certain conditions of hydrogen gas concentration, temperature, pressure, and so on. After polymerization, the catalyst-containing polymer is separated from the reaction mixture and transferred to a second reactor, where further polymerization takes place under different conditions.

[0082] Components (A) and (B) may be produced using any catalyst system, preferably a coordination catalyst such as a Ziegler-Natta catalyst system, preferably a coordination catalyst such as a Ziegler-Natta transition metal catalyst from Groups III-Χ of the Periodic Table (IUPAC), metallocene, non-metallocene, as is known in the art. An example of a preferred Ziegler-Natta catalyst includes Ti, Mg and Al as described in EP 0 688 794 B1, which is hereby incorporated by reference in its entirety. It is a highly active pro-catalyst containing a specific inorganic support, a supported cross-linking compound, the cross-linking compound being the same or different from the titanium compound, the inorganic support being brought into contact with a metal alkyl chloride that is soluble in a non-polar hydrocarbon solvent. and has the formula (R._nMeCl3-n) m, where R is a C1 -Co-alkyl group, Me is a metal from group 111 (13) of the periodic table, n = 1 or 2, and m = 1 or 2, to obtain the product of the first reaction, and the product of the first reaction contacting a compound containing a hydrocarbon radical and a hydrocarbon oxide radical bound to magnesium, which is soluble in the polar hydrocarbon solvents, to obtain a second reaction product, and the product of the second reaction is contacted with a chlorine-containing titanium compound having the formula ChTKOR¹⁷) ^, where R.^IV is a CH-hydrocarbyl group and x = or 4, to obtain a pro-catalyst. Preferred supports are inorganic oxides, more preferably silicon dioxide or silica. Most preferably, silica having an average particle size of 20 µm is used. Even more preferably, triethylaluminum is used as cocatalyst. Alternatively, a metallocene of a Group IV metal may be used.

[0083] Preferably, polymer (A), a low molecular weight (LMW) polymer, is produced with or without comonomer added in the first reactor, as well as polyolefin (B), a high molecular weight (HMW) polymer, is produced from with or without additive, more preferably with additive, comonomer in the second reactor.

[0084] The final product obtained consists of a homogeneous mixture of polymers from two reactors, the different molecular weight distribution curves of these polymers together forming a molecular weight distribution curve having a broad maximum or two maximums, i.e. the end product is a mixture of multimodal or bimodal polymers. As multimodal and, in particular, bimodal polymers, preferably ethylene polymers and their production belong to the prior art, no detailed description is given here, but reference is made to the above-mentioned WO 92/12182. It can be seen that the order of the reaction steps can be reversed.

[0085] Preferably, as stated above, the multimodal polymer composition of the invention is a bimodal or trimodal polymer composition. Equally preferably, a bimodal or trimodal polymer composition is prepared by the polymerization as described above under different polymerization conditions in two or more series connected polymerization reactors.

[0086] Furthermore, it is advantageous to use the process as defined above for the preparation of the multimodal composition according to the invention in which

1. a) the polymer (A) and polyolefin (B) are produced together in a multistage process comprising a loop and a gas phase reactor, polymer (A) being produced in at least one loop reactor and polyolefin (B) being produced in a gas-phase polymerization reactor in the presence of reaction product (A) in a loop reactor, and

2. b) the filler (C) and the composition containing the polymer (A) and polyolefin (B) are mixed together until they are combined.

[0087] In particular, the multistage process described above is used. The loop reactor is particularly preferably operated at a temperature of from 75 to 100 ° C, more preferably in the range of 85 to 100 ° C and most preferably in the range of 90 to 98 ° C. The pressure is preferably from 58 to 68 bar, preferably from 60 to 65 bar.

[0088] Preferably, polymer (A) is prepolymerized in the first loop reactor and then continuously transferred to a second loop reactor, where polymer (A) is further polymerized. Preferably the temperature in the second loop reactor is from 90 to 98 ° C, more preferably around 95 ° C. The pressure is preferably 58 to 68 bar, more preferably approximately 60 bar.

[0089] Furthermore, it is preferred that in the second loop reactor the concentration of ethylene is from 4 to 10 mol%, more preferably from 5 to 8 mol%, and most preferably about 6.7 mol%.

[0090] The molar ratio of hydrogen to ethylene is highly dependent on the catalyst used. It must be adjusted to obtain the desired melt flow rate MFR of the polymer withdrawn from the loop reactor. For the preferred catalyst described herein, it is preferred to use a hydrogen to ethylene mole ratio of from 100 to 800 mol / kmol, and more preferably from 300 to 700 mol / kmol, even more preferably from 400 to 650 mol / kmol, and most preferably about 550 mol / kmol.

[0091] The polymer suspension is then preferably removed from the loop reactor using settlers and then preferably introduced into a vessel operating at about 3 bar, where the polymer separates from most of the liquid phase. The polymer is then preferably transferred to a gas phase reactor operating preferably at a temperature of 75 to 95 ° C, more preferably 80 to 90 ° C, and most preferably about 85 ° C, and preferably at a pressure of 10 to 50 bar, more preferably 15 to 25 bar, and most preferably about 20 bar.

[0092] Furthermore, ethylene comonomers are used and hydrogen and nitrogen as inert gas are preferably introduced into the reactor, such that the ethylene fraction in the fluidizing gas is preferably from 1 to 10 mol%, more preferably from 1 to 5 mol%, and most preferably about 2.5 mole% and the ratio of hydrogen to ethylene is preferably from 100 to 400 mol / kmol, more preferably from 150 to 300 mol / kmol, and most preferably about 210 mol / kmol.

[0093] The comonomer to ethylene ratio affects the desired density of the bimodal polymer. Hence, preferably the comonomer to ethylene ratio is from 20 to 150 mol / kmol, more preferably from 50 to 100 mol / kmol, and most preferably about 80 mol / kmol. Preferably, the polymer is removed from the gas phase reactor and then mixed with further additives such as antioxidants and / or processing stabilizers by agitation.

[0094] The blend of polymer (A) and polyolefin (B) is then mixed with filler (C) by any suitable method known in the art. These methods include combining the ingredients in a twin screw extruder, such as a counter rotating twin screw extruder or co-rotating twin screw extruder, and combining the ingredients in a single and poppy seed extruder.

[0095] Furthermore, the present invention includes a new multi-layer material comprising at least

1. a) a substrate as the first layer (I) and

2. b) the multimodal polymer composition described above as at least one further layer (II).

[0096] Preferably, the multi-layer material consists of

1. a) the substrate as the first layer (I) and

2. b) the multimodal polymer composition described above as at least one further layer (II).

[0097] Further preferably, the multi-layer material is a two-layer or three-layer material consisting of a substrate as the first layer and a polymer composition for the second and third layers, preferably at least the second layer is the polymer composition as defined above. The layers can of course be in any order. Optionally, this multi-layer material includes adhesion promoters such as tetraisopropyl titanate, tetrastearyl titanate, tetrakis (2-ethylhexyl) titanate, poly (dibutyl titanate).

[0098] Preferably, the substrate is selected from the group consisting of paper, cardboard, aluminum foil and plastic foil.

[0099] Preferably, the multi-layer material comprises low-density polyethylene (LDPE) as further layer (III). In this connection, preferably the low density polyethylene has a density of 900 to 950 kg / m3³, more preferably from 915 to 925 kg / m2³. Moreover, preferably the low density polyethylene (LDPE) melt flow rate MFR2 is from 2.0 to 20.0 g / 10 min, more preferably from 3.0 to 10.0 g / 10 min.

[0100] Preferably, the coating mass of layer (III) comprising the polymer composition of the present invention is in the range of 5 to 60 g / m2²and more preferably from 10 to 45 g / m2². Moreover, preferably the layer (III) comprising low density polyethylene (LDPE) described above has a coating with a weight of 0 to 25 g / m 2.², more preferably from 3 to 18 g / m2².

[0101] The present invention also includes a film, preferably a cast film, comprising the multimodal polymer composition described above, and more preferably the film consists of the multimodal polymer composition of the invention.

[0102] Furthermore, the present invention provides a method of producing a multi-layer material comprising the inventive polymer composition described above. Accordingly, it is preferred that the multimodal polymer composition described above is applied to a substrate by a coating line including a decoiler, a rewinder, a cooling drum and a coating head. Preferably, the advancing speed of the coating line is in the range 50 to 5000 m / min, more preferably 100 to 1500 m / min. The coating can be made with any line known in the art. Preferably, a coating line with at least two extruders is used which is capable of producing multilayer coatings from different polymers. It is also possible to adapt a line to treat the polymer melt exiting the die to improve adhesion, e.g. by ozone treatment, corona discharge or flame treatment.

[0103] Furthermore, the present invention encompasses the use of the multimodal polymer composition as defined above for extrusion coating, in particular for extrusion coating to produce a multilayer material as described above.

[0104] Furthermore, the present invention relates to the use of a multimodal polymer composition for films, preferably cast films.

[0105] Below, the present invention is illustrated by way of examples.

Examples

Measurement

WVTR:

[0106] The water vapor transmission rate was measured at 90% relative humidity and 38 ° C according to the ASTM E96 method.

Base weight or coating weight:

[0107] The base weight (or coating weight) was determined as follows: Five samples were cut parallel to the line direction from the embossed coated paper. The size of the samples was 10 cm x 10 cm. The samples were dried in an oven at 105 ° C for one hour. The samples were then weighed and the coating weight was calculated as the difference between the base weight of the coated structure and the base weight of the substrate. The results were given as the weight of the material per square meter.

Average molecular weights and molecular weight distribution:

[0108] Average molecular weights and molecular weight distribution were determined according to ISO 16014, part 2 universal calibration (narrow MWD polystyrene standards (universal calibration) and using a set of 2 mixed-bed columns + 1 × 10⁷ A Tosohas (JP).

Density:

[0109] The density was determined according to ISO 1183-1987.

Melt index or melt index:

[0110] The melt flow rate (also referred to as melt index) was determined according to ISO 1133, at 190 ° C. The load used in the measurement is indicated as subscript, ie MFR2 is the MFR measured with a load of 2.16 kg.

Melt flow ratio:

[0111] The melt flow ratio is the ratio of the melt flow rates measured at different loads, i.e. FRR5 / 2 is the ratio of MFRs to MFR₅.

Coiling:

[0112] Curl was determined by cutting circular samples having an area of ​​100 cm² within two hours of coating. The sample is then allowed to shrink freely on the stage for two minutes. The curl is measured as the difference (in mm) from the table to the folded sheet.

Example 1

[0113] A dry granule blend was made from 650 kg CA8200 low density polyethylene with 300 kg Finntalc MO5SL talc filler, manufactured and sold by Mondo Minerals and 50 kg Clariant PP6100 PP wax. This blend was then mixed until combined and pelletized using the above-mentioned ZSK70 extruder. The melt temperature during extrusion was 200 ° C. The composition was then dried at 60 ° C for 6 hours to remove the moisture. CA8200 is a low density polyethylene designed for extrusion coating, manufactured and marketed by Borealis. It is produced by free radical polymerization in a high pressure autoclave. It has an MFR2 of 7.5 g / 10 min and a density of 920 kg / m3³. Clariant PP6100 is a low molecular weight propylene polymer having a number average molecular weight of 2090 g / mol, a weight average molecular weight of 5,370 g / mol, a z-average molecular weight of 10,900 g / mol, and a DSC softening point of 109 ° C. The composition has a density of 1195.7 kg / m3³ and MFR2 6.1 g / 10 min.

Comparative example 1

[0114] The procedure of Example 1 was repeated, except that the amount of CA 8200 was 700 kg and Clariant PP6100 was not used. Moreover, no drying was performed at 60 ° C.

Table 1: Data for compositions containing polyolefins and talc used in cast films.

<td>Example</td><td>Composition</td><td>MFR2 g / 10 min</td><td>Density 920 kg / m³</td>

<td>Example 1</td><td>LD / PP / talc</td><td>ON</td><td>ON</td>

<td>Comparative example 1</td><td>LD / - / talc</td><td>ON</td><td>ON</td>

NA - Does not apply

Example 2

[0115] The composition of Example 1 was used to make a lab scale film (in Collin laboratories) on a cast film production line containing a monolith and poppy-seed extruder with a screw diameter of 30 mm and a length to diameter (L / D) ratio of 30. Speed line travel was 10 m / s (from 8.9 to 10.3 m / s), efficiency 5 kg / h (from 4.91 to 6.07 kg / h), head temperature 250 ° C and melt temperature 70 ° C (68 to 72 ° C). Data are presented in Table 2.

[0116] The thickness of the film was 45 µm. The WVTR was 5.0 g / m2²/ 24 h.

Example 3

[0117] The procedure of Example 2 was repeated, except that the film thickness was 98 µm. The WVTR was 2.3 g / m2²/ 24 h.

Comparative example 2

[0118] The procedure of Example 3 was repeated, except that the composition of Comparative Example 1 was used in place of the composition of Example 1. Data is provided in Table 2.

Table 2: Data for cast films.

<td>Example</td><td>Composition</td><td>Thickness pm</td><td>WVTR g / m²/ 24 hours</td>

<td>Example 2</td><td>LD / PP / talc</td><td> 45</td><td> 5,0</td>

<td>Example 3</td><td>LD / PP / talc</td><td> 98</td><td> 2,3</td>

<td>Comparative example 2</td><td>LD / - / talc</td><td> 102</td><td> 2,7</td>

Borealis Technology Oy; Finland

Proxy:

EP 1 836 232 B2

Z-8190/16